Increase In Xanthine Oxidase Activity Research Articles

Pteridine and tryptophan pathways in children with type 1 diabetes: Isoxanthopterin as an indicator of endothelial dysfunction

AimType 1 diabetes (T1D) and its complications are known to be associated with oxidative stress. Pteridine derivatives and indoleamine 2,3-dioxygenase (IDO) activity can be used as biomarkers in the evaluation of oxidative stress. In this study, our aim is to compare the concentrations of serum and urinary pteridine derivatives, as well as serum IDO activity, in children and adolescents diagnosed with T1D and those in a healthy control group. MethodA cross-sectional study was performed and included 93 patients with T1D and 71 healthy children. Serum and urine biopterin, neopterin, monapterin, pterin, isoxanthopterin, and pterin-6-carboxylic acid (6PTC) and serum tryptophan and kynurenine levels were analyzed and compared with healthy controls. High-performance liquid chromatography was used for the analysis of pteridine derivatives, tryptophan, and kynurenine. Xanthine oxidase (XO) activity, a marker of oxidative stress, was defined by measurement of serum and urine isoxanthopterin. As an indicator of indolamine 2,3-dioxygenase (IDO) activity, the ratio of serum kynurenine/tryptophan was used. ResultsSerum isoxanthopterin and tryptophan concentrations were increased, and serum 6PTC concentration was decreased in children with T1D (p=0.01, p=0.021, p<0.001, respectively). In children with T1D, IDO activity was not different from healthy controls (p>0.05). Serum neopterin level and duration of diabetes were weakly correlated (p=0.045, r=0.209); urine neopterin/creatinine and isoxanthopterin/creatinine levels were weakly correlated with HbA1c levels (p=0.005, r=0.305; p=0.021, r=0.249, respectively). Urine pterin/creatinine level negatively correlated with body mass index-SDS. (p=0.015, r=-0.208). ConclusionWe found for the first time that isoxanthopterin levels increased and 6PTC levels decreased in children and adolescents with T1D. Elevated isoxanthopterin levels suggest that the XO activity is increased in TID. Increased XO activity may be an indicator of vascular complications reflecting T1D-related endothelial dysfunction.

Heterocyclic compounds as xanthine oxidase inhibitors for the management of hyperuricemia: synthetic strategies, structure-activity relationship and molecular docking studies (2018-2024).

Hyperuricemia is characterized by higher-than-normal levels of uric acid in the bloodstream. This condition can increase the likelihood of developing gout, a form of arthritis triggered by the deposition of urate crystals in the joints, leading to inflammation and pain. An essential part of purine metabolism is played by the enzyme xanthine oxidase (XO), which transforms xanthine and hypoxanthine into uric acid. Despite its vital role, diseases such as gout have been associated with elevated uric acid levels, which are linked to increased XO activity. To manage hyperuricemia, this study focuses on potential nitrogen based heterocyclic compounds that may serve as XO inhibitors which may lower uric acid levels and prevent hyperuricemia. Xanthine oxidase inhibitors are a class of medications used to treat conditions like gout by reducing the production of uric acid. The present study demonstrates numerous compounds, particularly nitrogen containing heterocyclic compounds including their synthesis, structure-activity relationship, and molecular docking studies. This paper also contains drugs undergoing clinical studies and the xanthine oxidase inhibitors that have been approved by the FDA.

The Effects of Xanthine Oxidase Inhibitors on the Management of Cardiovascular Diseases

The Effects of Xanthine Oxidase Inhibitors on the Management of Cardiovascular Diseases

The role of melatonin in preventing amiodarone-induced rat liver damage.

Long-term exposure to amiodarone, an antiarrhythmic drug, can induce different organ damage, including liver. Cell damage included by amiodarone is a consequence of mitochondrial damage, reactive oxygen species production, and cell energy depletion leading to programmed cell death. In the present study, hepatoprotective potential of neurohormone melatonin (50mg/kg/day) was evaluated in a chronic experimental model of liver damage induced by a 4-week application of amiodarone (70mg/kg/day). The obtained results indicate that amiodarone induces an increase in xanthine oxidase activity, as well as the content of the lipid and protein oxidatively modified products and p53 levels. Microscopic analysis further corroborated the biochemical findings revealing hepatocyte degeneration, apoptosis, and occasional necrosis, with the activation of Kupffer cells. Coadministration of melatonin and amiodaron prevented an increase in certain damage associated parameters, due to its multiple targets. In conclusion, the application of melatonin together with amiodarone prevented an increase in tissue oxidative damage parameters and moderately prevented liver cell apoptosis, indicating that the damage of hepatocytes provoked by amiodarone supersedes the protective properties of melatonin in a given dose.

Does Monosodium Urate Crystal Vascular Deposition Exist? Review of the Evidence

Cardiovascular disease in gout is a central issue, but the underlying mechanisms linking the two are unclear. The existence of monosodium (MSU) crystal deposition directly inflaming vessel walls has been recurrently suggested and challenged since the 1950s and is again a matter of active debate since recent studies using dual-energy computed tomography (DECT) suggested a higher prevalence of plaques considered to be containing MSU crystals in patients with gout. The objective of this review is to critically cover the evidence gathered on MSU crystal deposition in the cardiovascular system. In patients affected with gout, histological evidence of MSU crystals in arteries lacks a biochemical characterization supporting the observation in polarized light microscopy, while current knowledge on vascular lesions identified in DECT as containing MSU crystals suggests that they may be only artifacts, including in cadaveric and phantom studies. In individuals without gout, MSU crystal deposition in vessel walls have not been demonstrated, despite higher urate local plaque concentrations and increased xanthine oxidase activity. Gout is associated with increased arterial calcification and atherosclerosis, both being potential confounders of suspected MSU crystal deposition for the analysis of DECT scans and histopathology, respectively. In summary, the reality of the presence of MSU crystals in vascular plaques has not been demonstrated so far, and needs further investigation as it represents a potential outcome for cardiovascular complications of gout.

Hepatic Ischemia-reperfusion Injury: Protective Approaches and Treatment.

Ischemia and reperfusion damage to the liver is one of the major causes of hepatic dysfunction and liver failure after a liver transplant. The start of hepatic ischemia-reperfusion damage is linked to metabolic acidosis, Kupffer cells, neutrophils, excessive calcium, and changes in the permeability of the mitochondrial membrane. Hypoxia activates Kupffer cells, resulting in the production of reactive oxygen species (ROS). These ROS when accumulated, causes apoptosis and necrosis, as well as activate immune and inflammatory responses that involve many cells and signalling molecules. Numerous antioxidant compounds have been researched to lessen oxidative stress and thus serve as potential compounds to deal the ischemia-reperfusion damage. This article confers a deep understanding of the protective effects of some effective therapies, including hepatoprotective agents, attenuation of an increase in xanthine oxidase activity, and administration of antioxidants like N-acetylcysteine, superoxide dismutase (SOD), and ornithine.

Purine metabolism state in patients with type 1 diabetes mellitus

The aim of the study. To carry out a comprehensive analysis of the purine metabolism (PM) state and assess its features in patients with type 1 diabetes mellitus (DM). Materials and methods. 181 patients with type 1 DM were examined (94 women and 87 men) aged 42.5 ± 12.1 years. Indicators of the carbohydrate metabolism state, creatinine (Cr) concentration by the method of Popper, purine bases (PBs) and the activity of xanthine oxidase (XO) by a photometric method, uric acid (UA) by a colorimetric method were determined in fasting venous blood. UA excretion was detected by the colorimetric method, Cr by an enzymatic method. Renal UA clearance (RCUA), fractional UA clearance (FCUA), total UA tubular reabsorption (TTRUA) and hypoxanthine-guanine-phosphoribosyltransferase (HGPRT) activity were calculated. The comparison group, representative in terms of age and sex, included 25 healthy volunteers. Results. PM changes in patients with type 1 DM were orientated towards an excessively increased catabolism and insufficient reutilization of PBs. The structure of the detected disorders was as follows: hyperuricemia (HU) (13.8 %), enhanced RCUA (42.8 %), increased XO activity (35.6 %) and inhibition of HGPRT activity (53.3 %). In about 56 % of the subjects, high concentrations of PBs were found, and HU was diagnosed only in every seventh subject. It was identified that PB concentrations were negatively correlated with the level of XO activity. RCUA and XO activity levels were revealed to be of the greatest informational value for assessing the PM state in patients with type 1 DM. RCUA was significantly associated with the level of UA excretion and HGPRT activity. Relationships of RCUA and FCUA with HbAc1 levels were established. The higher the level of HbAc1, the greater the clearance of RCUA was, especially FCUA, which led to a significant decrease in TTRUA. Conclusions. PM in type 1 DM is characterized by a high intensity, which is realized due to a decrease in anabolism, increased oxidation and suppression of PB reutilization. Uricemia inadequately reflects the level of UA production in patients with type 1 DM. The severity of PM disorders in type 1 DM patients is associated with the carbohydrate metabolism compensation state.

Release of hepatic xanthine oxidase (XO) to the circulation is protective in intravascular hemolytic crisis

Xanthine oxidase (XO) catalyzes the catabolism of hypoxanthine to xanthine and xanthine to uric acid, generating oxidants as a byproduct. Importantly, XO activity is elevated in numerous hemolytic conditions including sickle cell disease (SCD); however, the role of XO in this context has not been elucidated. Whereas long-standing dogma suggests elevated levels of XO in the vascular compartment contribute to vascular pathology via increased oxidant production, herein, we demonstrate, for the first time, that XO has an unexpected protective role during hemolysis. Using an established hemolysis model, we found that intravascular hemin challenge (40 μmol/kg) resulted in a significant increase in hemolysis and an immense (20-fold) elevation in plasma XO activity in Townes sickle cell phenotype (SS) sickle mice compared to controls. Repeating the hemin challenge model in hepatocyte-specific XO knockout mice transplanted with SS bone marrow confirmed the liver as the source of enhanced circulating XO as these mice demonstrated 100% lethality compared to 40% survival in controls. In addition, studies in murine hepatocytes (AML12) revealed hemin mediates upregulation and release of XO to the medium in a toll like receptor 4 (TLR4)-dependent manner. Furthermore, we demonstrate that XO degrades oxyhemoglobin and releases free hemin and iron in a hydrogen peroxide-dependent manner. Additional biochemical studies revealed purified XO binds free hemin to diminish the potential for deleterious hemin-related redox reactions as well as prevents platelet aggregation. In the aggregate, data herein reveals that intravascular hemin challenge induces XO release by hepatocytes through hemin-TLR4 signaling, resulting in an immense elevation of circulating XO. This increased XO activity in the vascular compartment mediates protection from intravascular hemin crisis by binding and potentially degrading hemin at the apical surface of the endothelium where XO is known to be bound and sequestered by endothelial glycosaminoglycans (GAGs).

Role of Serum Uric Acid in Metabolic Syndrome: A Cross-sectional Study in Central Karnataka

Abstract Background: Elevated levels of uric acid are the end product of purine metabolism. Uric acid levels are regulated by xanthine oxidase enzyme. Increased xanthine oxidase activity results in the generation of free radicals. Hence, elevated uric acid levels are the manifestations of oxidative stress. Meanwhile, raised uric acid can trigger release of inflammatory mediatory and create the inflammatory state. Thus, inflammation and oxidative stress are the important events in the pathogenesis of metabolic syndrome. This study aimed to find the association of uric acid levels with metabolic syndrome and the individual components of metabolic syndrome. Methodology: A comparative, descriptive, cross-sectional study was conducted among 50 metabolic syndrome cases and 50 controls. Clinical examination followed by laboratory investigations for the estimation of serum uric acid, fasting blood sugar, postprandial blood sugar, glycated hemoglobin, high sensitivity C-reactive protein (Hs-CRP), fasting insulin, and lipid profile. Insulin resistance (IR) was calculated by homeostatic model assessment-IR (HOMA-IR). Results: In the metabolic syndrome patients’ group, serum uric acid was found to have strong positive correlation with body mass index, blood pressure, glycemic indices, IR, lipid profile, and Hs-CRP. It was found that there was 2.5 times higher risk of development of metabolic syndrome with every unit increase in serum uric acid levels and this association was found to be statistically significant. Conclusion: Uric acid can be used as the marker for the early identification of metabolic syndrome or as a prognostic marker in the diagnosed cases of metabolic syndrome.

The prognostic impact of uric acid in acute heart failure according to coexistence of diabetes mellitus

Background and aimsIncreased uric acid levels predict higher mortality in heart failure (HF) patients. Patients with diabetes mellitus (DM) appear to have increased xanthine oxidase activity. We aimed to study if the association between uric acid and mortality in acute HF was different according to the coexistence of DM. Methods and resultsWe studied a cohort of patients hospitalized due to acute HF in 2009–2010. Patients with no uric acid measurement upon admission were excluded from the analysis. Follow-up: 2 years; endpoint: all-cause mortality. Patients with elevated uric acid (>80.0 mg/L) were compared with those with lower values. We used a multivariate Cox-regression analysis to assess the prognostic impact of uric acid (both continuous and categorical variable: cut-off 80.0 mg/L). The analysis was stratified according to coexistence of DM. We studied 569 acute HF patients, 44.6%male, mean age 76 years, 290 were diabetic. Median admission uric acid: 81.2 mg/L and 52.2%had uric acid >80.0 mg/L. Elevated uric acid predicted all-cause mortality in acute HF only in patients with DM. The multivariate-adjusted HR of 2-year mortality was 1.68 (95 % CI: 1.15–2.46) for diabetic HF patients with uric acid>80.0 mg/L compared to those with lower levels (p = 0.008) and 1.10 (95 % CI: 1.03–1.18) per each 10 mg/L increase in uric acid (p = 0.007). In non-diabetic HF patients, uric acid was not associated with mortality. ConclusionsIncreased uric acid predicts ominous outcome in acute HF patients with diabetes, however, it is not prognostic associated in non-diabetics. Uric acid may play a different role in acute HF depending on DM status.

Sodium-glucose co-transporter 2 inhibitors in heart failure with preserved ejection fraction: reasons for optimism.

Sodium-glucose co-transporter 2 inhibitors in heart failure with preserved ejection fraction: reasons for optimism.

Chronic Febuxostat Treatments Prevents Cerebrovascular Dysfunction Associated with Chronic Stress

Chronic stress is a risk factor for many cerebrovascular diseases including stroke and vascular dementia. Our lab has previously shown that chronic stress impairs cerebrovascular function potentially mediated by an increase in oxidative stress driven by the xanthine oxidase pathway. However, the therapeutic avenues of the xanthine oxidase inhibitor, febuxostat have yet to be examined in the context of chronic stress induced cerebrovascular dysfunction. Here, we examined the effect of chronic febuxostat treatment on middle cerebral artery function in a mouse model of chronic stress. At 18 weeks of age, mice underwent the unpredictable chronic mild stress (UCMS; 5 days/weeks for 7hrs/day) paradigm to elicit a chronic stress phenotype; simultaneously, drinking water was treated with febuxostat (50mg/L) and provided to mice ad libitum (n=9-10/group). On week 26 mice were euthanized and the middle cerebral arteries (MCA) were removed and positioned in a pressurized myobath. To test for vessel health, the MCA was exposed to increasing concentrations of acetylcholine (Ach; 10-9M to 10-4M), phenylephrine (PE; 10-9M to 10-4M), and sodium nitroprusside (SNP; 10-9M to 10-4M). Consistent with previous work, mice exposed to chronic stress with no treatment displayed impaired MCA dilation to Ach compared to controls (8.4±0.8um to 19.7±0.8um, respectively; p<0.0001). Interestingly, mice exposed to chronic stress while simultaneously treated with febuxostat displayed comparable MCA dilation to Ach compared to controls (18.6±0.4um to 19.7±0.8um, respectively; n.s.). There were no differences found between groups in response to PE or SNP. These data suggest that the cerebrovascular dysfunction associated with chronic stress may be driven by increased xanthine oxidase activity.

Abstract P60: Xanthine Oxidase Mediates Cerebrovascular Dysfunction in Chronically Stressed Female Mice

Chronic stress is a risk factor for many cerebrovascular diseases including stroke and vascular dementia. Our lab has preciously shown that chronic stress in male mice and rats reduces cerebrovascular function, mediated by an increase in oxidative stress, potentially via the xanthine oxidase pathway. However, the role of xanthine oxidase on cerebrovascular function in female mice has yet to be explored. Here, we examined the effect of chronic stress on middle cerebral artery function and xanthine oxidase expression in female mice. At 18 weeks of age, mice underwent the unpredictable chronic mild stress (UCMS; 5days/week for 7hrs/day) paradigm to elicit a chronic stress phenotype. On week 26, mice were euthanized and the middle cerebral arteries (MCA) were removed and positioned in a pressurized myobath. To test for vessel health, the MCA was exposed to increasing concentrations of acetylcholine (Ach; 10-9M to 10-4M) in the presence or absence of febuxostat (10uM), a xanthine oxidase inhibitor as well as increasing doses of phenylephrine (PE; 10-9M to 10-4M) and sodium nitroprusside (SNP; 10-9M to 10-4M). Coronal sections of brain tissue were then stained for the xanthine oxidase enzyme, imaged using a Nikon Eclipse 800 and fluorescence intensity was analyzed via ImageJ. MCA dilation to Ach was impaired in female mice that underwent UCMS compared to control mice (9.5±1um vs 20±1um; p&lt;0.05). Incubating the MCA with febuxostat had no effect on control mice but improved MCA dilation in the UCMS mice (9.5±1um to 17±0.5um; p&lt;0.05). No differences were found between control vs UCMS groups in response to PE or SNP. To support this, preliminary data (n=3-4/group) shows a trend of increased fluorescence intensity of xanthine oxidase expression within the somatosensory cortex of the mice exposed to UCMS compared to controls (41,666±2,923AU vs 31,091±3,759AU, respectively; p=0.059). Together, these data suggest increased xanthine oxidase activity plays a role in cerebrovascular dysfunction in female mice.

Selenium and alpha-tocopherol reduces ϑluoride induced oxidative stress in brain and muscle of mice

Fluoride is one of the common environmental pollutants. Its excessive exposure results in a wide array of toxicity phenotypes including oxidative stress, skeletal and soft tissue damage etc. Antioxidants such as Selenium (Se) and α-tocopherol are attractive agents for oxidative stress prevention because of their safety profile and wide availability. It is known that in combination, Se and alpha-tocopherol act synergistically against ROS formation. This study investigated the protective effects of selenium (05 µg/kg BW) and Alpha-tocopherol (2 mg/kg BW) on markers of oxidative stress in brain and muscle of mice exposed to sodium fluoride (20mg/kg BW) for 15 days. The results showed significant (p&lt;0.05) alterations in markers of oxidative stress includes; an increase in xanthine oxidase activity and lipid peroxidation, a decline in SOD, CAT, GST and GPx activities in fluoride exposure group in comparison with control group indicates oxidative stress induced by fluoride. These changes were reversed modestly in Se and alpha-tocopherol alone treated groups and significantly (p&lt;0.05) in the combinedly treated group indicating synergistic action in mitigation of fluoride effect.

Xanthine Oxidase Has a Protective Role during Heme Crisis By Binding and Degrading Heme

Xanthine oxidase (XO) is a key enzyme in the purine degradation pathway, catalyzing the catabolism of hypoxanthine to xanthine and xanthine to uric acid. A byproduct of these reactions is the generation of the reactive oxygen species (ROS), hydrogen peroxide and superoxide. XO is produced primarily in the liver; however, following hepatic stressors such as inflammation, hypoxia, or ischemia, XO is released from the liver and enters the circulation. XO can then bind distal endothelium via electrostatic interactions with glycosaminoglycans (GAGs). Current dogma believes that XO plays a harmful role in pathologies due to the increase in ROS production that can alter signaling pathways and damage endothelial cells. XO activity has been shown to be elevated in a number of hemolytic conditions including, sickle cell disease, malaria, and sepsis; however, the involvement of XO in these pathological conditions has not been fully elucidated. These conditions result in increased hemolysis, releasing free heme and hemoglobin into the circulation, inducing an inflammatory response, and damaging endothelial cells. Identifying the involvement of XO during heme crisis could improve our understanding of the pathologies associated with hemolytic conditions and lead to the identification or development of more effective treatment options. We hypothesized that XO has damaging properties under basal conditions; however, the presence of XO is crucial and protective during heme crisis by serving as a secondary mechanism of heme degradation when canonical heme degradation pathways are saturated. In order to explore the role of XO in heme crisis, we developed a novel heme crisis model in which we pre-treated mice with the clinically relevant dose of 10 mg/kg/day febuxostat, an FDA approved XO inhibitor, for five days in drinking water. Following inhibition of XO, the mice were challenged with two identical doses of hemin one hour apart and monitored for 24 hours. We observed a 20-fold increase in XO activity in the mice treated with 50 μmol/kg hemin. This increase was completely inhibited in the mice treated with febuxostat. Surprisingly, the febuxostat treated mice had worsened survival compared to the untreated mice. This suggests a protective role for XO during heme crisis. We hypothesized that XO has a protective role by preventing platelet activation and degrading excess free heme. To investigate this hypothesis, we used flow cytometry to quantify heme-induced platelet activation. Healthy human platelets were isolated and treated with 2.5 μM hemin, 10 mU/mL XO, 200 μM hypoxanthine, and 20 μM febuxostat. We observed 72% activation with heme alone, while incubation with XO and hypoxanthine resulted in almost complete prevention of platelet activation (16%). We were also able to partially restore platelet activation (45%) when febuxostat was added. Based on these results, we hypothesize that XO binds GAGs on the platelet surface and degrades heme in order to protect platelets from heme-induced activation. To assess the ability of XO to degrade heme, we tested whether XO binds heme. We performed computational modeling in which we identified a potential heme binding site in the FAD domain of XO with a kd = 128 nM. We confirmed heme-XO binding by performing a heme binding assay. We incubated heme (25 μM) alone, heme + XO (50 μM), and heme + XO + hypoxanthine (100 μM) for 20 minutes. Heme binding was assessed by dot blotting in nitrocellulose followed by chemiluminescent detection and dot density quantification. We observed a 2-fold increase in dot density when heme and XO were incubated and a 4-fold increase with heme, XO, and hypoxanthine. These results support a potential heme-XO interaction that is amplified when the enzyme is active. Lastly, we measured XO's ability to degrade heme using UV visible spectrophotometry. We incubated hemin, XO, and hypoxanthine together and measured the absorbance over 20 minutes. We observed a decrease in absorbance at 618 nm, indicative of heme degradation. In conclusion, contrary to the current dogma, we have identified a potential protective role for XO during hemolytic crisis. We found that febuxostat treatment worsened survival in heme challenged mice, XO prevented heme-induced platelet activation, identified a potential heme-XO binding site, and observed XO-induced heme degradation. XO may have a protective role in hemolytic conditions by serving as a secondary mechanism of heme degradation. Disclosures No relevant conflicts of interest to declare.

Febuxostat attenuates testosterone-induced benign prostatic hyperplasia in rats via inhibiting JAK/STAT axis

AimTo investigate the possible modulatory effect of febuxostat in testosterone-induced benign prostatic hyperplasia (BPH) in rats with emphasis on xanthine oxidase (XO)/Janus Kinases (JAK)/signal transducer and activator of transcription (STAT) axis. Main methodsMale Wistar rats were treated with testosterone with/out febuxostat. Effect of febuxostat on BPH was assessed at the structural level by histopathology and determination of prostate weight/index. Cyclin D1 protein expression was assessed immunohistochemically and the ratio of Bax/Bcl-2 mRNA expression was determined by real time polymerase chain reaction analysis (RT-PCR). Besides, uric acid serum level was determined colorimetrically. Prostatic XO activity, as well as oxidative stress and inflammatory markers were evaluated. Additionally, western blot analysis was performed for determination of JAK-1 and phosphorylated form of STAT-3 expression in tissues. Key findingsResults revealed that febuxostat inhibited the increase in prostatic weight and index compared to testosterone-treated group. Additionally, febuxostat ameliorated testosterone-induced histopathological changes, prevented the rise in cyclin D1 expression and enhanced Bax/Bcl2 ratio. Febuxostat suppressed testosterone induced- increase in XO activity in prostates and serum level of uric acid. Moreover, it regulated oxidative stress markers including; malondialdehyde (MDA), superoxide dismutase (SOD) activity and glutathione (GSH) content. Also, it inhibited the increase in prostate contents of interleukin-6 (IL-6), interleukin-1β (IL-1 β), tumor necrosis factor (TNF-α) and nuclear factor (NF-κB). Interestingly, febuxostat markedly reduced JAK-1 and subsequent phosphorylation of STAT-3 protein expression. SignificanceFebuxostat ameliorates testosterone-induced BPH via suppressing XO/JAK/STAT axis. This may help to re-purpose the use of XO inhibitors.

Lifeceramics-treated water reduces serum uric acid levels and improves hemorheological activity in hyperuricemic rats.

Lifeceramics (LC) is made of zeolite and oyster shell and is hypothesized to act as an anti-oxidative agent. In the present study, the effects of LC-treated water (LC water) on the concentration of serum uric acid (SUA) and the hemorheological parameters in male rats with hyperuricemia (HUA) was assessed. To prepare LC water, distilled water was mixed with LC particles. HUA was induced in rats by daily potassium oxonate (PO) injection (250 mg/kg). The PO-injected rats were separated into three different groups and were administered distilled water (PO rats), allopurinol [a xanthine oxidase (XOD) inhibitor] solution [PO + allopurinol (AP) rats] or LC water (PO+LC rats) by gavage. Control rats were intraperitoneally injected with sodium carboxymethyl cellulose solution and administered untreated distilled water by gavage. After injection and gavage for 5 weeks, the SUA concentration, hemorheology index and antioxidant index were measured. The SUA concentration and blood deformation index of the PO rats were significantly higher and lower, respectively, compared with the control rats. However, in the PO+LC rats, the SUA concentration and blood deformation index decreased and increased, respectively, to a level similar to that of the control as well as that in the PO+AP rats. Furthermore, the PO-induced increase in XOD activity was suppressed by combined treatment with LC water, resulting in a decrease in malondialdehyde concentration. These results suggest that LC water can reduce the SUA concentration, increase serum antioxidant activity and improve hemorheological activity in hyperuricemic rats.

561-P: Activated Xanthine Oxidase in Serum Is a Potent Therapeutic Target for Experimental Diabetic Polyneuropathy

Xanthine oxidase (XO), a potent inducer of reactive oxygen species, catalyzes purine metabolism. XO is expected to be implication of the macrophage activation. XO is also expressed in the peripheral nerve system, while its role in diabetic polyneuropathy (DPN) has not been clarified. We explored the implication of XO in DPN of db/db mice (db/db) treating with XO-inhibitor, topiloxostat (To). C57BL6 mice (C57) and db/db (5 wks of age) were daily treated with 1mg/kg (dbT1) and 2mg/kg (dbT2) To (per os) for 8 wks. During experimental period, peripheral nerve function was monitored. At end, serum and dissected sciatic nerves and dorsal root ganglia (DRG) served for evaluation of uric acid metabolism. Primary culture of DRG neuron was performed to evaluate the effects of To on neurite outgrowth in vitro. To improved significant delay of nerve conduction velocities and elevation of threshold for tail flick test in db/db in a dose dependent manner (p&amp;lt;0.05 dbT2 vs. C57 for NCVs, p&amp;lt;0.05 db/db vs. dbT1, p&amp;lt;0.01 db/db vs. dbT2 for tail flick). XO activity was significantly up-regulated in DRG (p&amp;lt;0.01) and serum of db/db compared to those of W (p&amp;lt;0.05). To successfully suppressed the elevated XO activity in a dose dependent manner (p&amp;lt;0.05, W vs. T1, p&amp;lt;0.01, T1 vs. T2). Uric acid was significantly accumulated in serum and DRG of db/db compared to those of C57 (p&amp;lt;0.05). To could significantly reduce the accumulation (p&amp;lt;0.01). In primary culture of DRG neuron, extrinsic 100 μM XO depleted the neurite outgrowth more than 50 % than that of non-stimulated neurons (p&amp;lt;0.01). 4.3ng/ml To could significantly restored the reduction of neurite outgrowth compared to that of non-treated neurons (p&amp;lt;0.05). As a conclusion, increase in XO activity in serum and DRG may be implicated in the pathophysiology of DPN in db/db. Activation of XO in serum may directly exacerbate neuronal injury for DRG in DPN. To has a beneficial effect on DPN through its specific property to suppress serum XO activity. Disclosure H. Ichinohe: None. H. Mizukami: None. S. Osonoi: None. K. Kudo: None. S. Yagihashi: None.

Hereditary hemochromatosis disrupts uric acid homeostasis and causes hyperuricemia via altered expression/activity of xanthine oxidase and ABCG2.

Hereditary hemochromatosis (HH) is mostly caused by mutations in the iron-regulatory gene HFE. The disease is associated with iron overload, resulting in liver cirrhosis/cancer, cardiomegaly, kidney dysfunction, diabetes, and arthritis. Fe2+-induced oxidative damage is suspected in the etiology of these symptoms. Here we examined, using Hfe−/− mice, whether disruption of uric acid (UA) homeostasis plays any role in HH-associated arthritis. We detected elevated levels of UA in serum and intestine in Hfe−/− mice compared with controls. Though the expression of xanthine oxidase, which generates UA, was not different in liver and intestine between wild type and Hfe−/− mice, the enzymatic activity was higher in Hfe−/− mice. We then examined various transporters involved in UA absorption/excretion. Glut9 expression did not change; however, there was an increase in Mrp4 and a decrease in Abcg2 in Hfe−/− mice. As ABCG2 mediates intestinal excretion of UA and mutations in ABCG2 cause hyperuricemia, we examined the potential connection between iron and ABCG2. We found p53-responsive elements in hABCG2 promoter and confirmed with chromatin immunoprecipitation that p53 binds to this promoter. p53 protein was reduced in Hfe−/− mouse intestine. p53 is a heme-binding protein and p53-heme complex is subjected to proteasomal degradation. We conclude that iron/heme overload in HH increases xanthine oxidase activity and also promotes p53 degradation resulting in decreased ABCG2 expression. As a result, systemic UA production is increased and intestinal excretion of UA via ABCG2 is decreased, causing serum and tissue accumulation of UA, a potential factor in the etiology of HH-associated arthritis.

Altered activity of xenobiotic detoxifying enzymes at menopause – A cross-sectional study

Xenobiotic metabolism at menopause is an under-investigated topic, albeit women spend one-third of their life in the postmenopausal period. The present study examined the effect of menopause on the in vivo activities of CYP1A2, CYP2A6, xanthine oxidase (XO) and N-acetyltransferase-2 (NAT2) xenobiotic metabolizing enzymes. Enzyme activity was determined in 152 non-smoking volunteers following oral intake of a single dose of 200 mg caffeine and subsequent determination of caffeine metabolite ratios (CMRs) in a 6-h urine sample as follows: CYP1A2: (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X) and NAT2: AFMU/(AFMU+1U+1X). CMRs among groups were analyzed using one-way ANOVA. Significantly lower CYP1A2 and higher CYP2A6 CMRs were observed in postmenopausal compared to premenopausal women and age-matched men. These changes could be attributed to menopause rather than chronological aging since an age-related effect was not observed in premenopausal women or men of any age group. XO CMRs were higher in postmenopausal women and men>50 compared to premenopausal women and men<50, respectively, suggesting an age-related increase in XO activity. No significant alterations were discerned in NAT2 CMRs, in either slow- or rapid-acetylators, indicating that menopause exerts minimal modulation of xenobiotics metabolized by this enzyme. This study provides evidence that the transition to menopause induces significant alterations in xenobiotic-metabolizing enzymes independent of chronological aging suggesting altered metabolism of pharmaceutical and environmental agents.